1. Field of the Invention
This invention relates generally to tire features and more specifically, to the compositions forming decorative sidewall features and raised lettering on tires.
2. Description of the Related Art
Tires conventionally have rubber sidewalls made of rubber compositions reinforced with carbon black that are, therefore, black in color. Sometimes it is desirable to provide decorative features on a portion of the sidewall of a tire, such features made of a white colored or other light-colored rubber composition. These decorative portions include, for example, the white stripe of a whitewall tire and raised white lettering on the sidewalls of the tire. The rubber compositions used to form these decorative portions conventionally contain no carbon black and obtain their white coloring by the addition of titanium dioxide and mineral fillers or, for other light-colored features, other known coloring pigments.
Sidewalls of rubber tires may be subject to aging somewhat prematurely due to various factors which include (1) weathering due to atmospheric conditions such as, for example, exposure to ultraviolet light, ozone and high humidity; (2) fatigue cracking due to continual flexing of the tire sidewall under operating conditions; (3) abrasion due to scuffing against road curbs and other objects. Cracking can particularly be a problem in cold climates where temperatures are well below freezing for long periods of time. The decorative features on the sidewalls of tires are of special concern because, due to their white or other light coloring, blemishes on them may be more cosmetically observable than for black colored sidewalls.